instrument was not perfect enough to show the change of about a third of a minute which the precession of the equinoxes made in the declination while the star was visible, an amount which even his later and more perfect instruments would hardly have been able to point out.[1]
With the sextant Tycho was not able to observe the upper culmination of the star, at which it was only 6° from the zenith. As a supplement to his own results, he therefore gives in his later work[2] the observations made with the great quadrant at Augsburg by Paul Hainzel, which give a value of the declination agreeing within, a fraction of a minute with his own.
The observations with the sextant must have occupied Tycho during the winter of 1572-73, during which time the brightness of the new star had already commenced to decline considerably. When he first saw it, on the 11th November, it was as bright as Venus at its maximum brightness, and remained so during the month of November, so that sharp-sighted people could even see it in the middle of the day, and it could be perceived at night through fairly dense clouds. In December it was somewhat fainter, about equal to Jupiter; in January, a little brighter than stars of the first magnitude; and in February and March, equal to them. In April and May it was like a star of the second magnitude; in June, July, and August, equal to one of the third, so that it was very
- ↑ Progymn., p. 351. Individual results of observations are not given, and, unluckily, the original observations of Nova are lost; at least they are not in the volume of observations from 1563-81, repeatedly quoted. This only contains the following observations of Nova:—"1573 Die pentecostis 10 Maji inter flexuram Cassiopeæ et novam stellam 5g8′, 5g0′. Inter supremam cathedræ et novam stellam 5g28′, 5g20′. Inter Schedir et novam stellam 8g5′, 7g52′. Confide his observationibus subtracta tamen instrumenti parallaxi (5 gradus habent parallaxin 8 minutorum, 8 gradus habent 13).—Augusti die 14 inter novam stellam et Polarem 25g9′."
- ↑ Progymn., p. 360.
